Conventionally, in optical communications using an optical transmission member such as an optical fiber and an optical waveguide, optical modules including a light emitting element such as a surface-emitting laser (for example, a vertical cavity surface emitting laser (VCSEL)) have been used. Such optical modules include an optical receptacle that allows light which is emitted from a light emitting element and includes communication information to be incident on the end surface of an optical transmission member.
Some of the optical modules have a detecting element for monitoring the intensity or quantity of light emitted from a light emitting element, for the purpose of stabilization of output characteristics of the light emitting element or adjustment of optical output under temperature change (see, PTL 1).
PTL 1 describes an optical module which has a photoelectric conversion device including a light emitting element and a detecting element (light receiving element), and an optical receptacle optically connecting the light emitting element and the end surface of the optical transmission member (optical fiber). Further, the optical receptacle described in PTL 1 has a first surface on which light emitted from the light emitting element is incident and which emits monitor light toward the light receiving element, a first reflection surface which reflects the light emitted from the light emitting element and incident on the first surface, a light separation part which separate the light reflected on the first surface into monitor light travelling toward the first surface and light (signal light) to be coupled with the end surface of the optical fiber, and second surface which emits the light separated at the light separation part toward the end surface of the optical fiber.
In the optical module described in PTL 1, light which is emitted from the light emitting element and incident on the first surface is reflected on the first reflection surface to propagate toward the light separation part. The light which reaches the light separation part is separated thereat into signal light and monitor light. The monitor light is emitted from the first surface toward the light receiving surface of the light receiving element. The signal light is emitted from the second surface toward the light receiving surface of the optical fiber.
In an optical receptacle, an optical flat surface which transmits or reflects light affects sending and receiving of light, and therefore, it is necessary to control and measure the inclination angle of the optical flat surface with high accuracy. As a method for measuring an inclination angle of an optical flat surface of an optical receptacle with high accuracy, a method is known, by which the shape of a measuring object is measured in a noncontact manner using a laser probe (see, e.g., PTL 2).
PTL 2 describes a method and device for measuring the shape of a measuring object using a stage scanning type laser probe. The measuring device described in PTL 2 includes a laser light emitting unit, an objective lens, a focusing unit, a sensor, an auto focus (AF) scale, an X-stage and a Y-stage. A measuring object (a work to be measured) is disposed on the X-stage disposed on the Y-stage. The measuring object is then irradiated with laser light using the laser light emitting unit via the objective lens. Subsequently, reflected light which is reflected on the measuring object and transmitted through the objective lens again forms an image on the sensor. At this time, when focus is not on, the focusing unit moves the objective lens in the Z axis direction thereof to a focus point. The AF scale then detects the position (movement amount) of the objective lens. The shape of the measuring object can be measured based on the XYZ coordinate values of each detected point.